Final answer:
The somatotopy of the third neuron in the dorsal column pathway involves the body's spatial representation within the thalamus and cerebral cortex, with projections to the postcentral gyrus for sensory processing.
Step-by-step explanation:
The somatotopy of the third neuron in the dorsal column pathway refers to the spatial representation of the body within the central nervous system. Specifically, this term describes how different parts of the body are mapped onto different areas within the brain, such as the thalamus and cerebral cortex. In the dorsal column system, the third neuron's somatotopy is evident in its projection from the thalamus to the postcentral gyrus of the cerebral cortex, particularly in the organization of the medial lemniscus.
The third neuron receives input from the second neuron after it decussates in the medulla and ascends to the thalamus. The axons of these third neurons are then organized in such a manner that different areas of the postcentral gyrus correspond to specific parts of the body, enabling the somatosensory stimuli to be processed and perceived consciously.